The general concept of transmitting interrogating signals to coded objects and receiving coded or uncoded response signals is taught in U.S. Pat. Nos. 3,357,020; 3,805,265; 4,510,495; 4,466,125; 4,598,272; 4,598,275; 4,656,463; and 4,656,476. In U.S. Pat. No. 4,656,463 a system utilizing both passive and active transceivers is disclosed. Also, both electromagnetic (EMR) and ultrasound signals and Doppler effect ranging are disclosed. In U.S. Pat. No. 3,805,265 a radiant wave electronic locating system in which room sensors and a central console are linked by radiant energy signals is disclosed. The signals are coded and transmitted from the central console to track, locate or page a particular individual.
It is an object according to this invention to provide a system to help individuals with sensory deficiencies (e.g., blind or low vision) or mental confusion to find their way to desired objects or locations. It is a further object according to this invention to provide a system to remind an individual to get something (e.g., medicine) and to assist the individual in locating it. It is a further object of this invention to provide a system for directing a mobile robot with local object avoidance capability to a desired object or location.